Polyacetal copolymers are technically important macromolecules competitive with metals, ceramics and nylons in many applications. In the current technical processes, they are prepared by copolymerization of trioxane, with a comonomer such as ethylene oxide, dioxolane or butanediol formal. Each such copolymer molecule carries a maximum of two functional groups, e.g. hydroxyl end groups. For purposes such as preparation of graft copolymers and polymers with chemically bound stabilizers, it is desirable to synthesize polyacetals with higher levels of functional groups. It is an object of this invention to prepare polyacetal copolymers of trioxane that have stability equivalent to or greater than that of commercially available acetal copolymer while at the same time having functional groups which may be useful for further modifications or the attachment of additives.
In conventional acetal resin products, additives such as amidine thermal stabilizers and the like tend to reside in the amorphous regions of the polymer. Since the distribution of such non-crystalline areas is spatially random, the distribution of additives is often not optimal in terms of macroscopic properties. If functional sites can be provided at regular or semi-regular intervals (e.g. random copolymer) such that stabilizers or impact modifiers could be attached at a predetermined locus of points within the resin, then superior and more uniform properties could be achieved. This approach may be particularly advantageous since the crystal structure of acetal is such that additives are sterically obstructed from the crystalline areas. It therefore may be desirable to provide polymer backbone moieties that may disrupt the polymer's crystal structure in a controlled manner and provide a locus for attachment of additives.
Polyacetal copolymers with such backbone functional groups would be useful in many important applications such as: (a) preparing trioxane copolymers with chemically bonded stabilizers; (b) preparing trioxane copolymers with chemically attached impact modifiers; (c) preparing grafted copolymers of trioxane as compatibilizers with existing commercial acetal copolymer blends; (d) preparing copolymers amenable to surface modifications; and (e) preparing crosslinked copolymers.